A joining method for resin members to weld resin members together is known. (For example, see patent document 1.)
Disclosed in patent document 1 is a resin welding method for welding a first resin material that allows laser light to pass through, and a second resin material laminated to the first resin material, that absorbs and reflects laser light. With the resin-welding method described in patent document 1, initially, laser light that passes through the first resin material is radiated onto the second resin material when the first resin material and the second resin material are in a laminated state, thereby forming on the second resin material a deep-color portion having high-laser light absorbency. Thereafter, laser light is radiated onto the deep-color portion of the second resin material, thereby fusing the second resin material by that laser light being absorbed in the surrounding deep-color portion. With this configuration, the first resin material and the second resin material are welded.